The present invention relates to a wire cut electric discharge machine for machining a workpiece by causing electric discharge between a wire electrode, traveling between a pair of wire guides, and a workpiece immersed in dielectric fluid. In particular, the present invention relates to a wire cut electric discharge machine having an opening formed in a side wall of a work tank filled with dielectric fluid, one of the wire guides being attached to an arm extending through the opening. More particularly, the present invention relates to a seal for preventing leakage of dielectric fluid from the opening formed in the side wall of the work tank.
With many wire electric discharge machines, the wire electrode travels vertically between a pair of wire guides, and one of either the pair of wire guides or the workpiece moves in a horizontal Xxe2x80x94Y plane relative to the other. The workpiece is fixed to a work stand provided inside the work tank. The lower wire guide is attached to an end of an arm at a position lower than the workpiece. The arm extends through the opening formed in the side wall of the work tank.
As shown in FIG. 13, wire electric discharge machines having seals designed to prevent dielectric fluid leaking from an opening in a side wall of a work tank are already known. A work tank 40 is attached to a table 30. The table 30 is provided on a saddle 20, and is moveable in a Y axis direction. The saddle 20 is provided on a bed 10 and is moveable in the X axis direction, orthogonal to the Y axis. A workpiece WP is fixed to a work stand (not shown in the drawing) provided inside the work tank 40. A head 60 is attached to a column 50 positioned behind the work tank 40. A taper-cut unit 70 may be attached to the head 60, and an upper arm 80 is attached to the taper-cut unit 70. An upper guide assembly 81 having an upper wire guide is attached to a tip of the upper arm 80. A lower guide assembly 91 having a lower wire guide is attached to one end of the lower arm 90. A wire electrode EL bridges between upper and lower guide assemblies 81 and 91 perpendicular to the X axis and the Y axis. The upper guide assembly 81 is capable of moving in a horizontal U axis direction parallel to the X axis, and in a horizontal V axis direction parallel to the Y axis by the taper cut unit 70, so that the wire electrode EL may be tilted. A lower arm 90 extends outside of the work tank 40, and the other end of the lower arm 90 is fixed to the column 50. An opening 42, through which the lower arm 90 passes is formed in a side wall 41 of the work tank 40. The opening 42 extends in the X axis direction so that the work tank 40 can move in the X axis direction relative to the lower arm 90. In order to prevent leakage of dielectric fluid, a rigid slide plate 43 closing off the opening 42 is provided outside the work tank 40. A hole through which the lower arm 90 passes is formed in the slide plate 43. This hole has only a slightly larger diameter than the lower arm 90. An O-ring is provided in the small gap between the slide plate 43 and the lower arm 90. A resilient seal made of rubber or flexible plastic is provided between the slide plate 43 and the side wall 41. The slide plate 43 must have a length of twice the distance the work tank moves in the X axis direction, which causes the surface area for installation of the machine to be large. U.S. Pat. No. 4,647,747 discloses use of a closure strip made of a flexible material in place of the slide plate 43 of FIG. 13. In order to make the machine compact, both ends of this closure strip are wound using a reel. Japanese Patent No. 2651746 discloses a flexible closure strip that can be bent at corners of the side wall of the work tank, and a support member for supporting the closure strip against the pressure of the dielectric fluid. This support member is formed of several rigid plates linked together using a chain, so that it can be bent with the closure strip.
An object of the invention is to provide a compact and light weight seal that effectively prevents leakage of dielectric fluid inside the work tank.
Another object of the present invention is to provide a seal that can be easily manufactured.
According to one aspect of the present invention, a seal for preventing leakage of fluid from an opening formed in a side wall of a work tank of a wire electric discharge machine comprises:
a slide plate movable with respect to the work tank for closing the opening, and
a rail member attached to the work tank for guiding movements of the slide plate,
the slide plate having a waterproof flexible strip and a number of rigid blocks which are attached to the waterproof flexible strip and arranged in a row so as to engage with each other at the edges.
It is preferable that the rigid block has a convex edge such as a wedge-shaped edge, and a concave edge complementary to the convex edge.
It is preferable that the rigid block has a front surface comprising a non-bonding surface 6nd a bonding surface adopted to be coated with adhesive, the bonding surface projecting from the non-bonding surface, and a hole passing from a rear surface to the bonding surface. The adhesive may be injected from the hole to the bonding surface.
According to another aspect of the present invention, a method of manufacturing a slide plate for closing an opening formed in a side wall of a work tank of a wire electric discharge machine, comprises the steps of:
providing a waterproof flexible strip;
providing a number of rigid blocks, each of which has an injecting hole passing from the rear surface to the front surface;
sticking double-sided adhesive tape to the waterproof flexible strip in a longitudinal direction;
sticking the rigid blocks in a row to the flexible strip using the double-sided adhesive tape so that the edges of the adjacent rigid blocks are fitted together; and
injecting adhesive from the injecting hole to the front surface bounded by the double-sided adhesive tape to bond the rigid blocks to the waterproof flexible strip.
Additional objects, advantages and novel features of the invention will be set forth in the description that follows, and will in part become apparent to those skilled in the art upon reading this description or practicing the invention. The objects and advantages of the invention may be realized and attained by practicing the invention as recited in the appended claims.